In recent years, ferromagnetic dielectric (multiferroics) materials, in which a ferromagnetic property and ferroelectricity coexist and exhibit a composite action, have been receiving attention and actively researched and developed.
The ferromagnetic dielectric material is known to exert a so-called electromagnetic effect: the action of a magnetic field induces helical magnetic ordering to produce ferroelectricity, thereby generating electric polarization, or causing changes in electric polarization or dielectric constant; and the action of an electric field generates magnetization or causes changes in magnetization.
The ferromagnetic dielectric material which can, due to the electromagnetic effect mentioned above, cause changes in magnetization by an electric field and changes in electric polarization by a magnetic field, is thus expected to be applied to various types of ceramic electronic components such as variable inductors that change in magnetic permeability or magnetization through the application of an electric field, variable magnetization devices for writing heads of storage media, or magnetic sensors for detecting magnetism, and further non-volatile memories.
Furthermore, for example, Patent Document 1 proposes a multiferroic element where the orientation of electric polarization substantially orthogonal to an external magnetic field is adapted to be controlled by applying the external magnetic field to a multiferroic solid material that has both ferroelectricity and a ferromagnetic property that has a spin structure with a spin orientation rotating to follow the outside of a cone (the vertex of the cone has an opening angle α in the range of 0 degrees<α≤90 degrees).
In Patent Document 1, with the use of CoCr2O4 (M=Mn, Fe, Co, Ni) as a ferromagnetic dielectric material (multiferroic material), electric polarization is generated by the action of a magnetic field in the range of extremely low temperatures around 26 K, and electric polarization of 2 μC/m2 is obtained around 5 K.
In addition, Patent Document 2 proposes a multiferroic element adapted to induce an electric current by a weak external magnetic field of 300 gauss or less, with a multiferroic solid material containing an iron oxide as a main raw material, which has both ferroelectric and ferromagnetic properties.
Patent Document 2 mentions that when a low magnetic field of 300 G (0.03 T) acts with the use of a ferrite compound of Ba2Mg2Fe12O22 as a ferromagnetic dielectric material (multiferroic material), an electric current flow in response to the application of an alternating magnetic field at −268° C. (5 K), and electric polarization is also generated to alternate positive and negative.
Furthermore, Patent Document 3 proposes an electromagnetic effect material composed of, as a main constituent, an oxide ceramic represented by the general formula (Sr1−αBaα)3(Co1−βBβ)2Fe24O41+δ (where B represents one or more elements selected from the group consisting of Ni, Zn, Mn, Mg and Cu, and α, β, and δ respectively meet the formulas: 0≤α≤0.3, 0≤β≤0.3, and −1≤δ≤1), which has an electromagnetic effect in a temperature range of 250 to 350 K and in a magnetic field range of 0.05 T (tesla) or less.
In Patent Document 3, a ferromagnetic dielectric material that has a hexagonal Z-type crystal structure as represented by the above-mentioned general formula is achieved which has a domain with electric polarization of 1.0 to 9.5 μC/m2 and an electromagnetic coupling coefficient of 100 ps/m or more around room temperature and in a magnetic field range of 0.05 T or less, and up to 470 ps/m, obtained by sweeping between −0.05 T and +0.05 T with the use of the ferromagnetic dielectric material.
Patent Document 1: International Publication No. WO 2007/135817 (claims 1, 3, paragraph number [0031], FIG. 7, etc.)
Patent Document 2: Japanese Patent Application Laid-Open No. 2009-224563 (claims 1, 3, paragraph number [0032], FIG. 7, etc.)
Patent Document 3: Japanese Patent Application Laid-Open No. 2012-1396 (claim 1, paragraph numbers [0010], [0061], Table 3, FIG. 3, etc.)